added test_optimization to direct_Z3
added test_optimization to direct_Z3

hoangmle/metaSMT,finnhaedicke/metaSMT,hoangmle/metaSMT,agra-uni-bremen/metaSMT,nbruns1/metaSMT,finnhaedicke/metaSMT,agra-uni-bremen/metaSMT,finnhaedicke/metaSMT,hoangmle/metaSMT,nbruns1/metaSMT,agra-uni-bremen/metaSMT,nbruns1/metaSMT